Leading-particle suppression and surface emission in nucleus-nucleus collisions

After a short summary of the predictions of the Parton Quenching Model (PQM) for the nuclear modification factor and its centrality dependence in Au?Au collisions at RHIC, we concentrate on back-to-back jet-like correlations at high transverse momentum. We illustrate how this probe is biased by the surface effect.     

Superconductivity and possible overdoping in Lu1−x Ca x Ba2Cu3O7−δ

Structural and superconducting properties of the system Lu_1−x Ca _x Ba₂ Cu₃O_7−δ, both in bulk as well as thin film form, have been investigated. Presence of large Ca-ions at the Lu-sites is responsible for phase stability (in 1–2–3 phase) in bulk. In argon annealed tetragonal samples (δ:1) superconductivity is reinstated as in these samples, presence of Ca-ions lead to the generation of holes in the Cu−O planes. In oxygen annealed bulk samples and thin films, there is a large depression ofT _c due to divalent Ca-ions present in concentrationx<0.2. Our data indicate that this depression ofT _c is likely due to overdoping effect.     

Electrofission of 24Mg

The electron induced fission of ²⁴Mg leading to the ground states of two carbon nuclei has been studied using 25 to 45 MeV electrons. The observed sin²2θ angular distribution of the carbon nuclei indicates the dominance of E2 virtual photon absorption. The yield of ground state carbon nuclei is observed to decrease with increasing excitation energy in ²⁴Mg above 24 MeV.     

1,3-Adamantanyl dimethylsiloxane copolymers. Preparation and properties

1,3-bis(Dimethylhydroxysilyl)adamantane(I) has been prepared. Thermal condensation polymerization of this monomer yields poly-1,3-adamantyl-1,1,3,3-tetramethyldisiloxane. Condensation of I with bis(dimethylamino)dimethylsilane or 1,3-bis(dimethylamino)-1,1,3,3-tetramethyldisiloxane gave the expected 1,3-adamantyl dimethylsiloxane copolymers (II and III) respectively. These polymers have been characterized by ¹H,¹³C, and ²⁹SiNMR as well as GPC and TGA. They have unusually high thermal stability.     

Evolution of two-dimensional wormlike nanoclusters on metal surfaces

A pinch-off phenomenon is discovered in the evolution of 2D wormlike nanoclusters formed in homoepitaxial adlayers. This feature is shown to distinguish mass transport via periphery diffusion from other mechanisms. Continuum modeling of such evolution accurately describes experimental observations, particularly if one incorporates the anisotropy in step-edge line tension.     

Enhancement of relativistic harmonic generation by an optically preformed periodic plasma waveguide

Enhancement of relativistic third-harmonic generation by using an optically preformed periodic plasma waveguide was achieved. Resonant dependence of harmonic intensity on plasma density and density modulation parameters was observed, which is a distinct characteristic of quasi-phase-matching. The results demonstrate the potential of a modulated plasma waveguide in high-field applications.     

Feature extraction using molecular planes for fuzzy relational clustering of a flexible dopamine reuptake inhibitor

Six rigid-body parameters (Shift, Slide, Rise, Tilt, Roll, Twist) are commonly used to describe the relative displacement and orientation of successive base pairs in a nucleic acid structure. The present work adapts this approach to describe the relative displacement and orientation of any two planes in an arbitrary molecule-specifically, planes which contain important pharmacophore elements. Relevant code from the 3DNA software package (Nucleic Acids Res. 2003, 31, 5108-5121) was generalized to treat molecular fragments other than DNA bases as input for the calculation of the corresponding rigid-body (or "planes") parameters. These parameters were used to construct feature vectors for a fuzzy relational clustering study of over 700 conformations of a flexible analogue of the dopamine reuptake inhibitor, GBR 12909. Several cluster validity measures were used to determine the optimal number of clusters. Translational (Shift, Slide, Rise) rather than rotational (Tilt, Roll, Twist) features dominate clustering based on planes that are relatively far apart, whereas both types of features are important to clustering when the pair of planes are close by. This approach was able to classify the data set of molecular conformations into groups and to identify representative conformers for use as template conformers in future Comparative Molecular Field Analysis studies of GBR 12909 analogues. The advantage of using the planes parameters, rather than the combination of atomic coordinates and angles between molecular planes used in our previous fuzzy relational clustering of the same data set (J. Chem. Inf. Model. 2005, 45, 610-623), is that the present clustering results are independent of molecular superposition and the technique is able to identify clusters in the molecule considered as a whole. This approach is easily generalizable to any two planes in any molecule.     

Synthesis and biological activity of N-substituted-3-chloro-2-azetidinones

2-Aminobenzothiazole-6-carboxylic acid (1), on condensation with chloroacetyl chloride yielded 2-(2-chloroacetylamino)benzothiazole-6-carboxylic acid (2), which on amination with hydrazine hydrate yielded in turn 2-(2-hydrazinoacetylamino)benzo-thiazole-6-carboxylic acid (3). Compound 3, on condensation with various aromatic aldehydes afforded a series of 2-{2-[N'-(arylidene)hydrazino]acetylamino}benzothiazole-6-carboxylic acids 4a-h, which upon dehydrative annulation in the presence of chloroacetyl chloride and triethylamine yielded 2-{2-[3-chloro-2-(aryl)-4-oxoazetidin-1-ylamino]-acetylamino}benzothiazole-6-carboxylic acids 5a-h. The synthesized compounds 4a-h and 5a-h were screened for their antibacterial activity against four microorganisms: Staphylococcus aureus (Gram positive), Bacillus subtilis (Gram positive), Psuedomonas aeruginosa (Gram negative) and Escherichia coli (Gram negative). They were found to exhibit good to moderate antibacterial activity. The antifungal activity of these compounds were also tested against three different fungal species. None of them were active against the species tested.     

Activators of cylindrical proteases as antimicrobials: identification and development of small molecule activators of ClpP protease

ClpP is a cylindrical serine protease whose ability to degrade proteins is regulated by the unfoldase ATP-dependent chaperones. ClpP on its own can only degrade small peptides. Here, we used ClpP as a target in a high-throughput screen for compounds, which activate the protease and allow it to degrade larger proteins, hence, abolishing the specificity arising from the ATP-dependent chaperones. Our screen resulted in five distinct compounds, which we designate as Activators of Self-Compartmentalizing Proteases 1 to 5 (ACP1 to 5). The compounds are found to stabilize the ClpP double-ring structure. The ACP1 chemical structure was considered to have drug-like characteristics and was further optimized to give analogs with bactericidal activity. Hence, the ACPs represent classes of compounds that can activate ClpP and that can be developed as potential novel antibiotics.     

Studies on the Miscibility of Poly(2‐hydroxyethyl methacrylate) and Poly(ethylene oxide) Blends

Miscibility characteristics of poly[2‐hydroxyethylmethacrylate] (PHEMA) and poly[ethylene oxide] (PEO) have been investigated by solution viscometry, ultrasonic and differential scanning calorimetric (DSC) methods. The interaction parameters were obtained using the viscosity data. Ultrasonic velocity and adiabatic compressibility vs. blend composition have been plotted and are found to be linear. A single glass transition temperature was observed by differential scanning calorimetry. Variation of glass transition temperature (T_g) with composition follows Garden‐Taylor equation. T_g values have also been calculated from the Fox equation. The results obtained reveal that PHEMA forms a miscible blend with PEO in the entire composition range.